Fiber optic light panel assemblies include a light emitting panel member having one or more layers of optical fibers in close proximity to each other. Each optical fiber includes a light transmitting core portion of a suitable optically transparent material and an outer sheath of another optically transparent material having a relatively lower index of refraction than the core material to prevent the escape of light along its length. To cause light to be emitted from the optical fibers, the external surface of the optical fibers may be disrupted as by marring, abrading, scratching or otherwise causing mechanical, chemical or other disruptions at discrete locations along the length of the light panel. When light from one or more light sources is transmitted via one or more fiber optic light cables at one or both ends of the light panel, light will be emitted from the disrupted areas of the light panel. Such a panel assembly may be used to backlight a variety of devices including but not limited to keyboards, key pads, membrane switches, panels, and displays including liquid crystal displays and the like, to make them more discernible and enhance their visibility.
Such fiber optic light panel assemblies typically have a brighter area (i.e., a bloom area) adjacent the light receiving end(s) of the panel member because the light that is internally reflected in the cladding of the optical fibers as well as any high angle reflective light entering the panel member will immediately come out of the panel member where the cladding is first disrupted. A portion of the light entering the panel member may also travel the entire length of the panel member and exit out any non-lighted end of the panel member, creating a bright area at the non-lighted end of the panel member.
Also, if during the manufacturing process, the panel member is die cut to a desired size and shape to suit a particular application, the optical fibers along the die cut side edges of the panel member may be nicked by the cutting die or broken during subsequent handling, causing hot spots (i.e., bright spots) at the nicks or breaks. These hot spots along the side edges of the panel member may make the panel member unsuitable for certain applications especially where substantially uniform lighting throughout the panel member is a requirement for a particular application.
In some instances the panel member may be lighted using more than one light source. In that event, the optical fibers may not be properly distributed between the different light cables to compensate for any color differences or light output differences of the different light sources.
A need thus exists for a fiber optic light panel assembly and method of manufacture that eliminates bright areas at the ends of the panel member and hot/bright spots along the side edges of the panel member. Also a need exists to be able to compensate for any color differences and/or light output differences of two or more light sources used to light a fiber optic light panel assembly.